The present invention relates in general to a skive mechanism for stripping receiver members from fuser assembly rollers of reproduction apparatus, and more particularly to a fuser assembly roller skive mechanism which will substantially prevent damage to the skive fingers of the skive mechanism, or gouging of the surface of the rollers by the skive fingers.
In typical commercial reproduction apparatus (electrostatographic copier/duplicators, printers, or the like), a latent image charge pattern is formed on a uniformly charged dielectric member. Pigmented marking particles are attracted to the latent image charge pattern to develop such image on the dielectric member. A receiver member is then brought into contact with the dielectric member. An electric field, such as provided by a corona charger or an electrically biased roller, is applied to transfer the marking particle developed image to the receiver member from the dielectric member. After transfer, the receiver member bearing the transferred image is separated from the dielectric member and transported away from the dielectric member to a fuser assembly at a downstream location. There the image is fixed to the receiver member by heat and/or pressure from the fuser assembly to form a permanent reproduction thereon.
One type of fuser assembly, utilized in typical reproduction apparatus, includes at least one heated roller and at least one pressure roller in nip relation with the heated roller. The fuser assembly rollers are rotated to transport a receiver member, bearing a marking particle image, through the nip between the rollers. The pigmented marking particles of the transferred image on the surface of the receiver member soften and become tacky in the heat. Under the pressure, the softened tacky marking particles attach to each other and are partially imbibed into the interstices of the fibers at the surface of the receiver member. Accordingly, upon cooling, the marking particle image is permanently fixed to the receiver member.
It sometimes happens that the marking particles stick to the peripheral surface of the heated roller and result in the receiver member adhering to such roller; or the marking particles may stick to the heated roller and subsequently transfer to the peripheral surface of the pressure roller resulting in the receiver member adhering to the pressure roller. Therefore, a skive mechanism including skive fingers (or separator pawls) have been employed to engage the respective peripheral surfaces of the fuser assembly rollers to strip any adhering receiver member from the rollers in order to substantially prevent receiver member jams in the fuser assembly.
Typically a fuser assembly skive mechanism includes a plurality of skive fingers. The skive fingers are generally formed as elongated members respectively having a relatively sharp leading edge urged into engagement with a fuser assembly roller. For example, the skive fingers may be thin, relatively flexible, metal shim stock. The respective leading edge of each of the skive fingers is directed, in the opposite direction to rotation of the fuser assembly roller with which such skive finger is associated, so as to act like a chisel to strip any receiver member adhering to such roller from the peripheral surface thereof. However, if the marking particle image is particularly heavy, the receiver member may adhere to a fuser assembly roller with such force that engagement with the skive fingers does not completely strip the receiver member from the roller.
When a receiver member transported through the fuser assembly is only stripped from a roller by some of the skive fingers (and not by others), the receiver member will cause a jam in the fuser assembly. This destroys the reproduction formed on the receiver member and shuts down the reproduction apparatus. Moreover, as the receiver member moves with the fuser assembly roller to which it adheres, the stripped portions of the receiver member are forced into engagement with their associated skive fingers by the non-stripped portions of the receiver member. The engagement force of the receiver member on the skive fingers may be sufficient to flex those skive fingers so as to engage the associated peripheral surface of the fuser assembly roller at a substantially increased attack angle. This increased attack angle may then damage the roller by gouging its peripheral surface or may damage the skive finger itself. Alternatively, as the receiver member is transported through the fuser assembly, the receiver member may apply such force to the skive fingers on initial engagement therewith so as to cause such fingers to buckle in the direction which will flex those skive fingers to engage the associated fuser assembly roller at an increased attack angle. Again, this increased attack angle may damage the roller by gouging its peripheral surface or may damage the skive finger itself.